Egg yolk granules and phosvitin. Recent advances in food technology and applications

Egg yolk is consumed all around the world because of its nutritional and functional properties. It can easily be separated by centrifugation into two fractions, the egg yolk granules and plasma fractions. In comparison with the plasma fraction, the granular fraction has a low content of lipids and cholesterol and a high content of proteins; on the other hand, the lipid-rich plasma fraction has gelling and emulsifying properties similar to those of whole egg yolk. Therefore, taking into consideration their different composition and functional properties, it would be advantageous to increase the value of whole egg yolk by making different use of each of its fractions. In this sense, while the egg yolk plasma could, to some extent, be used as a substitute for whole egg yolk, the range of applications for the granules is more reduced at present and further research into this fraction is required to increase the interest of the food industry in the egg yolk fractionation process. The egg yolk granular fraction is mainly composed of globular proteins, namely lipovitellins or high-density lipoproteins, linked to phosvitin by phosphocalcium bridges. Phosvitin is the most phosphorylated protein found in nature, and shows remarkable metal chelating, antioxidant, emulsifying and antimicrobial properties and, owing to these capacities, it has also the potential to be isolated and incorporated by the food industry as a functional ingredient. Thus, the aim of the present review is to show the most recent advances in the food-related applications developed by the research community for egg yolk granules and their isolated components.